Method for the comminution of molten metals



Sept i8, H945. @,MJ, COMSTQCK 2,384,892

METHOD FOR THE COMMINUTION OF MOLTEN METALS Filed May 28, 1942 PatentedSept. 18, 1945 METHOD FOR THE COMMINUTION OF MOLTEN METALS Gregory J.Comstock, Summit, N. J., assignor to F. W. Berk & Company, New York, N.Y., a corporation of Maryland Application May 28, 1942, Serial No.444,868

6 Claims.

'I'he invention relates to a method for comminuting materials, moreparticularly metals and metallic alloys, and includes correlatedimprovements and discoveries whereby metals and metallic alloys may beobtained in iinely subdivided condition.

An object of the invention is the provision of a method in accordancewith which a material in molten condition may be comminuted orsubdivided as desired.

Another object of the invention is to provide a method for thecomminution of metals and metallic alloys, which may be readily,eiectively and economically carried out.

An additional object of the invention is to provide a method foreffecting comminution of metals and metallic alloys from the moltencondition.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others, all asexemplified in the following detailed disclosure, and the scope of theinvention will be indicated in the claims.

For convenience in description, the term metal will be used herein ascomprehending not only elemental metal, with or without ordinaryimpurities, and combinations of metals, but also metallic alloys ofvarious types, and it will be understood that where the term metal isused in this specification and in the appended claims, it has this broadsignificance unless the context otherwise clearly indicates.

The inveniton comprises bringing a material, illustratively a metal,into molten condition and to a suitable temperature, pouring the moltenmetal in a continuous but comparatively thin stream, and causing bodiesof liquid at moderate temperature having high kinetic energy to bombardthe stream of molten metal in rapid succession. By this method themolten metal is disintegrated into particles of minute size, each ofwhich is quickly chilled to a temperature below its freezing point.Liquids that may be used include water, carbon tetrachloride, alkalinesolutions, as dilute solutions of the hydroxides and carbonates ofsodium and potassium, and oils of high flash point and low viscosity, e.g., a hydrocarbon oil of relatively high boiling point.

An apparatus for carrying out the invention comprises means whereby ametal may be brought into a molten condition and to a desiredtemperature and poured in a continuous comparatively thin stream, incombination with means whereby high kinetic energy may be imparted tobodies of liquid and such bodies caused to bombard the stream of moltenmetal in rapid succession, together with means for collecting thedisintegrated metal and the liquid, which may then be separated.

The invention will be described in connection with an apparatus shown inthe accompanying drawing, which is diagrammatic only, but shows thenature and relationship of the components sufficiently to enable thoseskilled in the art to construct it readily.

In the drawing, I designates a melting pot which may be supplied withheat electrically by resistance windings or induction, or by other wellknown ways. 2 designates an orlce of relatively small diameter at a lowpoint in the bottom of the pot, through which molten metal may be pouredin a thin stream. The orifice 2 may be either hot or cold and controlledby a valve (not shown) of any well known type. A hot orifice in manyinstances is to be preferred in order to obviate chilling and possiblesolidification of the molten material. Such an orifice may be integralwith or separate from the melting pot and may comprise a sinteredzirconium oxide nozzle forming the lowermost part of a graphite vessel,as a crucible which may be heated by a suitably positioned electricheater, and enclosed, e. g., in a box containing an insulating material.The construction of the melting pot l and the orifice 2 will be chosenso as to be compatible with the metal to be treated and the temperaturesinvolved. If desired, the melting pot may be so arranged that it may becharged at one portion with massive metal in the solid state to bemelted continuously and supplied to the orifice for continuous pouring.It may also be provided with means for maintaining the molten metal,prior to pouring, at a desired predetermined temperature, e. g., a coilIl. The melting pot l may be so mounted that its position can beadjusted toward or away from the axis of the drum or rotor 3.

3 designates a rotatable drum or rotor supported by a shaft 4 providedwith a pulley 5 by which it may be driven rapidly by a suitable .sourceof power (not shown). The periphery of the drum is provided with aplurality of jet nozzles 6 equally spaced around its circumference.Liquid is supplied to the drum while it is rotating by a conduit l. Inoperation, centrifugal force drives the liquid supplied to the drum outthrough the jet nozzles 6 in iine streams, imparting to each particle ofliquid high kinetic energy. The nozzles maybe positioned at an angle ofabout 45.

8 designates an enclosing container, and 9 a cover. The cover may bemade substantially gas tight if the metal being treated requires thepresenc'e of a protective atmosphere within the container, and theappropriate gas introduced through suitable connections (not shown). Thecontainer 8 may be provided at a low point with a discharge outlet Iwhich may be controlled by a suitable valve Il, yand also with an outletI5, suitably positioned, whereby a desired liquid level may be set upand maintained. A hollow conduit I2 may surround the stream of moltenmetal issuing from the oriilce 2 to protect it from spray until it isclose to the point where it is to be bombarded by the ,iets of liquid. Anonoxidizing atmosphere may be set up in the hollow conduit throughintroduction by a pipe i3 of an illuminating gas, butane, nitrogen andthe like,

. whereby oxidation is obviated. This atmosphereA may be of a nature toeffect a reducing and/or carburizing action.

n carrying out the invention the metal to be comminuted may be melted ina crucible I6; introduced into the melting pot, and brought to andmaintained at a predetermined temperature. Power is applied through thepulley 5 to rotate drum 3 at a high rate of speed, and liquid issupplied to the drum through the pipe l. Centrifugal force acting on theliquid within the drum forces it out through the jet nozzles 6 in iinestreams of high velocity and consequently of high kinetic energy.

'Ihe orice 2 is now opened and the molten metal is poured in arelatively thin stream into the path of the rotating jets of liquid. Aseach jet moves across the path of the descending stream of molten metala small part of the jet bombards the metal and by its high kineticenergy breaks a'portion of the metal stream into minute particles, eachof which is immediately chilled to a temperature below its freezingpoint. After each jet has passed the path of the descending stream ofmolten metal, there is a brief interval of time during which the nextportion of the metal stream may descend into position to be bombarded bythe next Jet. The thus comminuted and solidified metal, together withany liquid which has not been evaporated, falls to the bottom of 'thecontainer 8, whence the mixture may be discharged at will through theoutlet I0. Any suitable method and apparatus may be utilized to separatethe liquid from the metal powder and dry the latter or otherwise prepareit for shipment or further use. Furthermore, it will be realized that a.plurality of streams of molten metal may be poured.

By this invention small bodies of liquid at moderate temperature butwith high kinetic energy are made to give up their kinetic energy tosmall bodies of molten metal where it is expended in disintegrating themolten metal into minute particles, and simultaneously the heat energyof the molten metal is transferred to the liquid, producing practicallyinstantaneous solidication of each particle. Somewhat more particularlythe method for comminution of a molten material, e. g. a molten metalcomprises forming a, stream of molten material, applying a succession ofsolid streams of liquid at a pressure not substantially less than 100pounds per square inch having linear motion and simultaneous transversemotion with respect to the stream of molten material to disintegrate theend thereof with formation oi minute particles, the liquid and thepositioning or the molten stream with respect thereto being such thatthere is a solid stream of liquid at the point of contact, successivecontacts being at a frequency greater than 200 per second, and the crosssectional areas of the molten stream and of the individual streams ofliquid being in a ratio such that substantially the entire end of thestream of molten material is swept by the solid streams of liquid toeftect its disintegration into minute particles.

Furthermore, when the speed of rotation is relatively high, the streamor streams of fluid produce the eilect of a rotating plane or atruncated cone depending upon the orientation or arrangement of thejets. Each portion of the plane or cone of iluid, as the case may be,is, however, in rapid linear motion in two directions, one being in thedirection of rotation and th-e other at an angle thereto. Also, a,regulation of the number of `iets and the speed of rotation makes itpossible to eiect a considerable variety of interruptions of the streamof molten material, as a metal. Thus, only one jet may be employedrotating at a relatively slow speed, or several jets may be utilizedwith a relatively high speed of rotation. A still further regulation maybe accomplished by increasing or decreasing the pressure of the fluidissuing from the jets, the result being to control the i'orce andcharacter of the comminuting effect exerted by the iluid throughinterruptive bombardment of a stream of molten material. Moreover,superposed series of streams of fluid may be used with which a stream ofmolten material may be successively bombarded in its downward path, andthe streams of the various series may be oriented in the same generaldirection, or the streams of one series may be directed substantiallyopposite to those of one or more of the other series.

As illustrations of ways in which the invention may be practiced, thefollowing examples are presented:

Example I A solder containing 50% lead and 50% tin and having a meltingpoint of about 370 F. was melted, heated to a temperature of about 800F., poured through an oriilce having a diameter of 9/64 inch, andsubjected to the action of jets of Water emerging from four jet nozzles,1A; inch in diameter, Ipositioned about a drum revolving at about 4000R. P. M. Water was introduced into the drum in volume sullicient tosupply an ample amount to the nozzles. The speed of rotation and numberof nozzles occasioned about 265 bombardments of the stream of moltenmetal per second, anda marked comminution of the solder was producedthereby.

Example II A solder, such as described in Example I, was melted andcomminution brought about in like `Example IV A solder was processed asin Example III, with like conditions, except that the jet nozzles had adiameter of il; of an inch.

'I'he comminuted material obtained in accordance with the foregoingexamples gave the following results respectively upon screen analysis,

U. S. Standard screens being employed:

Screen analysis lThese designations mean, e. g. -10:+20 that the amountsgiven pass through a No. 10 screen but are retained by a No. 20.

Example V Copper was melted and heated to a temperature of 2300 F.,poured through a heated orifice having a diameter of ifa inch andsubjected to the action of jets of water emerging from 16 jet nozzleshaving orifices 1A; inch in diameter positioned about a drum revolvingat about 6000 R. P. M. Water was introduced into the drum at a pressureof about 100 lhs. There were thus efiected about 1600 bombardments ofthe stream of molten metal per second. A high degree oi comminution ofthe copper resulted.

Example VI Brass was melted and heated to a temperature of 2100 F. andpoured through a hot orifice under the conditions prevailing in ExampleV, resulting in a high degree of comminution of the alloy.

Example VII Lead was melted and heated to a temperature of 800 F. andpoured through a hot orice under the conditions prevailing in Example V.The metal was nely subdivided.

Example VIII A mixture of metallic elements consisting of 90% by weightof silver and 10% lead was melted and heated to a temperature of about2300 F. with constant stirring. The melt was quickly poured through ahot orifice 1/8 inch in diameter and subjected to the action of jets ofwater similar to that described in Example V. This combination of metalswas thereby highly comminuted.

Example IX A mixture of metallic elements consisting of 90% copper and10% lead by weight was melted and heated to a temperature of about 2300F. with constant stirring. The melt was quickly poured through a hotorice .1/8 inch in diameter and subjected to the action o1 jets of watersimiar to that described in Example V. A high degree of comminution ofthe combination of metals resulted.

Screen analysis The foregoing procedures lead to comminution of a moltenmetal with production of a conslderable quantity of lines. Moreover, thematerial undergoing comminution may be siliceous, as a slag, a cement, aglass, and other meltable ceramic, or metallic, as the various metalsand combinations thereof both in the form of alloys, and where theconstituents do not form an alloy. more Iespecially lead, tin, cadmium,chromium, copper, aluminum, gold, silver, zinc, cobalt, irons, nickel;alloys, e. g., silver-cadmium. lead-tin, copper-boron, copper-beryllium,copper-zincl aluminumemagnesium; silver-tin, alloy steels,tinantimony-copper, bronzes, bismuth tin lead, sterling silver and caratgolds, and combinations as silver-lead, and copper-lead. It was observedthat as the number of jets was increased the amount of lines alsoincreased. When the speed of rotation is about 6000 R. P. M. and thenumber of jet nozzles sixteen, there is a distinct increase in theamount of fines obtained with an attending decrease in the amount ofcoarser material. Also, an increase in the amount of fines resulted whenthe distance between the stream of molten metal and the rotating jetnozzles was decreased. Furthermore, finer comminution of the metalresulted when the size of the stream of molten metal was reduced incomparison with the size of the liquid jets. There is, hence, a definiterelationship between the size of the metal stream and the size of theliquid jets.

The invention is characterized by the following factors:

(1) Since the stream of molten metal never comes in contact withanything except a liquid, there is no possibility of the metal stickingto and building up on solid metal parts.

(2) By selection of the number and size or jet nozzles on the drum, andits speed of rotation, and the distance between the nozzles and thestream of molten metal, a desired degree of fineness and a desireddistribution of ne and coarser particles may be achieved.

(3) The liquid used may be selected to exert a a desired eiect on themetal being treated, e. g., reduction, neutral behavior, oxidation,carburiza tion or decarburization. y

(4) Where the protection of the molten metal by an inert or reducingatmosphere is desirable provision can readily be made for introducingand maintaining such an atmosphere.

(5) VAlloys in powdered form may be produced containing much largerpercentages of one or more of the alloying elements than can be obtainedby conventional methods of melting and casting. A number of metals whichhave only limited solubility in other metals in the solid state aresoluble to a much greater degree in the liquid state, but segregationtakes place upon cooling in conventional processes. When such alloys inhigh percentages are subjected to the method of the invention, thedisintegration of the metal from the molten state is so complete and the'cooling of the disintegrated particles so rapid that the expectedsegregation does nottake place and the powder particles produced appearto be substantially homogeneous. Thus, by the method of the inventionpowdered metallic combinations may be produced with compositions andproperties unattainable by conventional procedures.

Since certain changes in carrying out the above method and which embodythe invention may be made without departing from its scope, it is in-.tended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not ina. limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of theI invention which, as amatter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

l. A method of producing comminuted material which comprises forming astream of molten material, applying a succession of solid streams ofliquid at a pressure not substantially lessthan 100 pounds per squareinch having linear motion and simultaneous transverse motion withrespect tothe streamof molten material to disintegrate the end thereofwith formation of minute Particles, the liquid and the positioning ofthe molten stream with respect thereto being such that there is a solidstream of liquid at the point of contact. successive contacts being at afrequency greater than 200 per second, and the cross sectional areas ofthe molten stream and of the individual streams of liquid being in aratio such that substantially the entire end of the stream of moltenmaterial 4is swept by the solid streams.

of liquid to eiect its disintegration into minute particles.

2. A method of producing comminuted material which comprisesl forming astream of molten metal, applying a succession of solid streams of liquidat a pressure not substantially less than 100 pounds per square inchhaving linear motion and simultaneous transverse motion with respect tothe stream of moltenv metal to disintegrate the end thereof withvformation of minute particles, the liquid and the position of the moltenmetal with respect thereto being such that there is a solid stream ofliquid at the point of contact, successive contacts being at a frequencygreater than 200 per second, and the cross-sectional areas of the moltenmetal and of the individual streams of liquid being in a ratio such thatsubstantially the entire end of thestream of molten metal is swept bythe solid streams of liquid to eiect its disintegration into minuteparticles.

3. A method of producing comminuted material which comprises forming astream of molten metal, applying a succession of solid streams of liquidat a pressure not substantially less than 100 pounds per square inchhaving linear motion and simultaneous transverse motion with respect tothe stream of molten metal to disintegrate the end thereof withformation of minute particles. the liquid and the position of the moltenmetal with respect thereto being such that there is a solid stream ofliquid at the point of contact. successive contacts being at a frequencygreater than 200 per 'second and at an angle of about 45, and thecross-sectional areas of the molten metal and of the individual streamsof liquid being in a ratio such that substantially the entire end of thestream of molten metal is swept by the solid streams of liquid to effectits disintegration into minute particles.

4. A method of producing comminuted metal which comprises melting analloy containing lead and tin, pouring the molten metal in a continuousstream, applying a succession of solid streams of liquid at a pressurenot substantially less than pounds per square inch having linear motonand simultaneous transverse motion with respect to the stream of moltenmetal to disintegrate the end thereof with formation of minuteparticles, the liquid and the position of the molten metal with respectthereto being such that there is a solid stream of liquid at the pointof contact, successive contacts being at a frequency greater than 200per second. and the cross-sectional areas of the molten metal and of theindividual streams of liquid being in a ratio such that substantiallythe entire end of the stream of molten metal is swept by the solidstreams of liquid to effect its disintegration into minute particles. I

5. A method of producing comminuted metal which comprises melting amixture of copper and lead, pouring the molten metal in a continuousstream, applying a succession of solid streams of liquid at a pressurenot substantially less than 100 pounds per square inch having linearmotion and simultaneous transverse motion with respect to the stream ofmolten metal to disintegrate the end thereof with formation of minuteparticles, the liquid and the positioning of the molten metal streamwith respect thereto being such that there is a solid stream of liquidat the point of contact, the successive contacts being at a frequency ofabout 1600 per second, and the cross-sectional areas of the molten metalstreamand of the individual streams of liquid beingr substantiallyequal.

6. A method of producing comminuted metal which comprises meltingcopper, pouring the molten metal in a continuous stream, applying asuccession of solid streams of liquid at a pressure not substantiallyless than 100 pounds per square inch having linear motion andsimultaneous transverse motion with respect to the stream of moltenmetal to disintegrate the end thereof with formation of minuteparticles, the liquid and the positioning of the molten metal streamwith respect thereto being such that there is a solid stream of liquidat the point of contact, the successive contacts beng at a frequency ofabout 1600 per second, and the cross-sectional areas of the molten metalstream and of the individual streams of liquid being substantiallyequal.

GREGORY J. COMSTOCK.

